This invention relates generally to methods and apparatus for logging earth boreholes and specifically to methods and apparatus which allow the logging of highly deviated and very hot earth boreholes.
It has become relatively common within the last few years to drill wells in the search for oil and gas and the like with a portion of the bore deviating from the usual vertical orientation thereof. The deviation or inclination may extend for a considerable distance at angles ranging to 70.degree., sometimes returning to the usual vertical orientation. In some instances, such boreholes may even extend past 90.degree. from the vertical and actually be extending in the upward direction for some distance.
It is also well known in the art of drilling such wells to attempt the logging of the formation surrounding such boreholes with logging instruments run into the well bore on a wireline and/or cable to perform various operations. Such tools usually depend upon the force of gravity to permit the positioning of the well tool at the desired formation in the well bore.
Manifestly, the relatively horizontal angle of the deviated portion of the well bore will not permit the wireline-actuated tools to move into the lower portion of the well bore since friction of the well tool in the deviated portions works against the force of gravity. Thus, it becomes essential to provide some means for causing a well logging instrument to pass through the deviated portions of the well bore.
Another problem associated with such boreholes relates to the instability of some formations penetrated by the well bore, thus causing borehole diameter changes, some very abrupt. Ledges are formed, and the logging instruments sometimes lodge against them.
Those skilled in the art will recognize that there have also been systems which pump well logging instruments down through the drill pipe and that only certain well logging systems, for example, those using radioactivity, can be utilized since they are effective whether within or without the drill pipe. However, other types of well logging instruments cannot be effectively utilized inside the drill pipe, for example, those using acoustic, resistivity, induction and the like measurements which are unduly influenced by the drill pipe itself.
It is therefore the primary object of the present invention to provide new and improved methods and apparatus for logging deviated boreholes in which it is difficult for the well logging instrument to transverse the borehole simply with the aid of gravity.
It is yet another object of the present invention to provide new and improved method and apparatus for logging very hot wells.
The objects of the invention are accomplished, generally, by methods and apparatus which utilize a flexible hose pumped down through the interior of the drill pipe and through which logging instruments are caused to transverse the earth formations beyond the lower end of the drill pipe.
These and other objects, features and advantages of the present invention will be apparent from the following detailed description taken with reference to the figures of the accompanying drawing, wherein: